Explanation:
Light emitted by a planet far beyond
our Solar System
has been identified for the first time.
The planet, illustrated in the
above drawing, had its light detected by comparing
the brightness of only the parent star,
when the planet was
behind the star,
to the light emitted when both the
planet and its parent star were visible.
The Earth-trailingSpitzer Space Telescope made the observation in
infrared light, where the intrinsic glow of the
planet outshines the light it reflects from its central star.
The direct observation
of light allowed a measurement of both the temperature and
size of the planet:
HD 209458b.
Planet HD 209458b was confirmed to be larger than expected
for its mass and on an orbit around its
parent star that was unexpectedly close to a
circle.